全文获取类型
收费全文 | 75402篇 |
免费 | 15053篇 |
国内免费 | 6167篇 |
专业分类
化学 | 68424篇 |
晶体学 | 812篇 |
力学 | 2991篇 |
综合类 | 367篇 |
数学 | 7182篇 |
物理学 | 16846篇 |
出版年
2024年 | 127篇 |
2023年 | 755篇 |
2022年 | 1306篇 |
2021年 | 1496篇 |
2020年 | 2572篇 |
2019年 | 3795篇 |
2018年 | 2181篇 |
2017年 | 1865篇 |
2016年 | 4878篇 |
2015年 | 5071篇 |
2014年 | 5356篇 |
2013年 | 6659篇 |
2012年 | 6254篇 |
2011年 | 5772篇 |
2010年 | 5245篇 |
2009年 | 5071篇 |
2008年 | 4945篇 |
2007年 | 4155篇 |
2006年 | 3694篇 |
2005年 | 3502篇 |
2004年 | 2855篇 |
2003年 | 2526篇 |
2002年 | 3191篇 |
2001年 | 2389篇 |
2000年 | 2102篇 |
1999年 | 1241篇 |
1998年 | 816篇 |
1997年 | 720篇 |
1996年 | 757篇 |
1995年 | 612篇 |
1994年 | 569篇 |
1993年 | 498篇 |
1992年 | 481篇 |
1991年 | 445篇 |
1990年 | 356篇 |
1989年 | 314篇 |
1988年 | 246篇 |
1987年 | 197篇 |
1986年 | 221篇 |
1985年 | 216篇 |
1984年 | 155篇 |
1983年 | 111篇 |
1982年 | 107篇 |
1981年 | 86篇 |
1980年 | 83篇 |
1979年 | 79篇 |
1978年 | 66篇 |
1976年 | 61篇 |
1974年 | 61篇 |
1973年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
K. Y. Lin 《Journal of statistical physics》1987,49(1-2):269-279
The spontaneous magnetization of the Ising model on a 4–8 lattice with six different coupling constants and two different magnetic moments is studied. A formula for the spontaneous magnetization is proposed. The result agrees with the exact low-temperature series expansions up to the 12th order. 相似文献
82.
Let V be a hypersurface with an isolated singularity at the origin in ? n+1. It is a natural question to ask when V is defined by weighted homogeneous polynomial or homogeneous polynomial up to biholomorphic change of coordinates. In 1971, a beautiful theorem of Saito gives a necessary and sufficient condition for V to be defined by a weighted homogeneous polynomial. For a two-dimensional isolated hypersurface signularity V, Xu and Yau found a coordinate free characterization for V to be defined by a homogeneous polynomial. Recently Lin and Yau gave necessary and sufficient conditions for a 3-dimensional isolated hypersurface singularity with geometric genus bigger than zero to be defined by a homogeneous polynomial. The purpose of this paper is to prove that Lin-Yau’s theorem remains true for singularities with geometric genus equal to zero. 相似文献
83.
Lin Surong 《Annals of Differential Equations》2006,22(4):517-523
The singularly perturbed boundary value problem for nonlinear higher order ordinary differential equation involving two small parameters has been considered. Under appropriate assumptions, for the three cases:ε/μ2→0(μ→0),μ2/ε→0 (ε→0) andε=μ2, the uniformly valid asymptotic solution is obtained by using the expansion method of two small parameters and the theory of differential inequality. 相似文献
84.
85.
86.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
87.
介绍了原子力显微镜在生物物理领域的最新应用:蛋白质去折叠、DNA拉伸、生物膜受力,通过分析实验得到的力谱,可以获取关于蛋白质、DNA、生物膜结构信息.原子力显微镜不仅能反映测量体系的力学性质,由于其具有独特的时间、空间分辨及实时成像,因而能提供更多信息. 相似文献
88.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
89.
90.
Natural populations, whose generations are non-overlapping, can be modelled by difference equations that describe how the populations evolve in discrete time-steps. In the 1970s ecological research detected chaos and other forms of complex dynamics in simple population dynamics models, initiating a new research tradition in ecology. However, in former studies most of the investigations of complex population dynamics were mainly concentrated on single populations instead of higher dimensional ecological systems. This paper reports a recent study on the complicated dynamics occurring in a class of discrete-time models of predator–prey interaction based on age-structure of predator. The complexities include (a) non-unique dynamics, meaning that several attractors coexist; (b) antimonotonicity; (c) basins of attraction (defined as the set of the initial conditions leading to a certain type of an attractor) with fractal properties, consisting of pattern of self-similarity and fractal basin boundaries; (d) intermittency; (e) supertransients; and (f) chaotic attractors. 相似文献